Electric light bulb unit



July 16, 1957 J. B, DlcKsoN 2,799,795

ELECTRIC LIGHT BULB UNIT Filed July 22, 1955 /g-"nnnnnnnn'n k A JNVENTOR. L 77- .5 Z'CSON.

BYMWWMW United States Patfif 2,799,795- ELECTRIC 'LIGHT' Bunn' John B. Dickson', Lughltmdl Park, Mien., assigner to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Applieatiun Jury 22; 1953, sei-'tal No; 369,684

z claims. (ci. 313:-31-85 This invention relates' to an' improved electric light bulb.

An object of the invention is to provide improvements in an electric light bulb unit which facilitate detachably securing the same to a support therefor having an opening. The unit is preferably of the type including a filament containing bulb part projecting from one end of a base part and secured thereto, the bulb part having a diameter so predetermined as to accommodate its insertion through the support opening and travel of the base portion into the opening for threaded engagement with the wall bounding such opening.

More particularly the invention has for its object to provide in such a unit an improved base part which can be economically manufactured and which facilitates its engagement with the support. In a more speciiic aspect of the invention the base part has a section which is of uniform diameter and has a threaded external surface which mounts the unit relative to the support by threading the section into the support opening. The threaded surface is of a character which effects a locking or wedging engagement with the support to securely mount the unit and limit travel of the base part section into the support opening.

As an illustrative embodiment for carrying out the foregoing and as a further object of the invention, the external threading for the base section of uniform diameter is characterized by a groove which varies in depth at successive groove convolutions, and more preferably the groove decreases in depth in a direction toward that end of the base part opposite to the bulb part. Such thread characteristic may be included in the wall of the support opening although a normal, uniform thread appears to be satisfactory with the thread of the base section having the varying groove depth. In either way, the varying groove depth produces a wedging action with the support which securely mounts the unit to the support and limits travel of the base into the support opening. The wedging produces a radial force component directed mainly to the base of the thread groove. In this embodiment the pitch of the threads of the base section is preferably constant but the root dimension of these threads varies, such dimension decreasing with the decrease in groove depth.

Other objects and advantages of the invention will be more apparent from the following description taken in conjunction with the following drawings, in which:

Fig. 1 is an enlarged elevational View, partly in section, of an electric light bulb unit embodying the invention.

Fig. 2 is a longitudinal sectional view, in elevation, of the unit shown in Fig. l.

The electric bulb unit includes a bulb part 5 and a metallic base part 6 secured together by a body of basing cement 7 of insulating material. The bulb part 5 has a relatively small end extending into the base part 6, and while the latter part is shown as filled with the basing cement 7, it Will be understood that the body of cement used can be confined to the telescoping portions of parts ICC 5 and 6 in securing the latter together. The end ofibarse 6 opposite the bulb receiving end has a closure 8, an edge` portion 9 of which is held in a channel section at 10 of the base. A hollow rivet 11 extends through an opening in the base and has its' inner and outer ends respectively flanged over the inner and outerl faces of the closure 8; theouter flange securing a conducting prong 12 to the closure, which prong 12 is adapted to be connected with a source of electrical energy.

The bulb 5 is provided with a filament 14 supported by a pair' of conventional conductors 15 one of which is connected with the rivet 11 and the other with the metallic base 6.

The;base 6 is shown as a metallic sleeve, a section 13 of which has a threaded" external surface anda uniform diameter. The unit is adapted to be secured to a support 16 having an opening 17 and the maximum diameter of the bulb part is sufficiently less than the diameter of the opening 17 and base section 13 to accommodate insertion of the bulb part through the opening and threading of the base section therein. The support is extended at the opening to provide an axial sleeve 18 although the wall bounding the opening may be merely the thickness of the support in case the latter is relatively large and may be sufficiently threaded to permit the desired threaded engagement of the support and base.

The unit is rmly secured to the support by wedging engagement of the threaded base section with the support, such engagement limiting travel of the base into the opening. This wedging engagement is effected by varying the depth of the thread groove at successive convolutions and this variation involves a variation in the root dimension at successive thread convolutions. The lines A-A of Fig. 2 exemplify the variation in thread groove depth, which is preferably gradual, from a maximum at the bulb end of base to a minimum in the direction of the opposite base end.

The lines B-B dene the outer diameter of the base section 13, which is preferably uniform, and in conjunction with lines A-A exemplify the decrease in the root dimension of successive thread convolutions in the direction away from the bulb end of the base. Preferably, the pitch of the threads of section 13 is constant and the threads of the Wall bounding the support opening are conventional.

The axial extent of the threaded surface 13 is much greater than that of the support wall and only a relatively small portion of the surface 13 Will be engaged with the wall of the opening when the unit is assembled to the support. The groove depth adjacent the bulb end of the base is so predetermined as to permit suflicient threaded travel of the base section 13 into the opening for support of the unit, and the decreasing depth of the groove which produce a wedging action in the base of the groove. That is, a thread convolution of the support Will bear against and Wedge With the base of the groove convolution of the section 13 and the thrust is substantially radial. Such wedging engagement assures a firm mounting of the unit relative to the support and limits threaded travel of the base into the support opening.

While the axial extent of the inter-threading and wedging engagement as shown is sucient for mounting the unit relative to the support nevertheless the additional threading and groove depth variation can be utilized to compensate for variation in diameter of the support opening.

The support Wall 16 may constitute a space enclosing wall or may be so related to other structure that the opening is accessible only from right to left as viewed in Fig. l and the illumination is desired at the left hand side of such wall. In either event the bulb part 5 is inserted in Patented July 16, 1957 Y Y a a direction from right to left through the opening for threading of the base sectionyl therein.

Iclaim: ,o o 5 Y1; An electric light bulb unit including a base part and a Yfilament*containing bulb part secured thereto, the Y base part including a portion having a uniform diameter and a threaded surface adapted for threaded engagement with a support, the diameter of said threaded surface of said base portion being larger than the diameter of said bulb part, the pitch of the threads of said surface being constant and the grooves of said threaded surface varying in depth. Y Y

-2. An electric light bulb unit including 'a base part and a` larnentV containing bulb part secured to the base part and projecting from one end thereof, the base part having a threaded section of uniform maximum outer diameter adapted for threaded engagement With the wall .bounding an opening in a .support for the unit, the pitch of the thread on said section being constant andthe grooves of said threaded section progressively decreasing in depth in an axial direction toward the other end of said base part for wedging engagement of the threaded section with the wall openingrto thereby limit travel of A the base part into the support opening.

Referencesl Cited in the tile of this patent UNITED STATES PATENTS 

